Study on countermeasure of infrasonic sound caused by rotating stall

Abstract

An infrasound sometimes occurs in an industrial field like a paper factory and it becomes a cause of complaints from neighborhood resident of the factory. The infrasound has acoustic features of a long wave length and little effects of conventional countermeasures such as an acoustic absorbent and sound insulator. Therefore once it happens, it has been difficult to do countermeasure. This paper describes that the rotating stall occurred in a fan (IDF: Induced Fan) becomes the cause of the infrasound generated from the EP (Electric dust collector) set in the factory. This is a very scarce and interesting phenomenon. So it is considered of value to describe the event. A lot of measurements were carried out to clarify the cause of this event. As a result, the cause of the infrasound is the resonance of the EP and the cause of the resonance is the rotating stall of the fan. Therefore the countermeasure is to exchange a new fan with P-Q characteristics of a large gradient (∂p/∂Q). As a result, the infrasound disappeared.

Keywords

• infrasound
• sound and acoustics
• rotating stall
• noise controll
• electric dust collector